The present invention relates to a steel laminate type cylinder head gasket for an internal combustion engine with an auxiliary combustion chamber.
In an engine with an auxiliary combustion chamber, a cylinder head is provided with a mouth plate to close the auxiliary combustion chamber. When the engine is operated, gas at first combusts at the auxiliary combustion chamber, and then gas at a cylinder bore combusts. Therefore, the mouth plate receives combustion pressure from both the auxilary combustion chamber and the cylinder bore.
As shown in FIGS. 1 and 2, a cylinder head J is provided with a depression K, to which a mouth plate L is inserted, so that an auxiliary combustion chamber M is defined inside the depression K. A gasket 10 is installed between the cylinder head J and a cylinder block P to seal therebetween. The mouth plate L is supported partly by a portion N of the gasket 10.
As stated above, when the engine is operated, combustion pressure is applied to the mouth plate L, so that large pressure is applied to the portion N of the gasket. Sometimes, the mouth plate L moves up and down.
In the conventional steel laminate gasket 10 as shown in FIGS. 1 and 2, the gasket 10 is formed of an upper plate, lower plate and three middle plates. A wire ring is installed around the cylinder bore Hc. Since the gasket 10 does not resiliently support the mouth plate, combustion gas is liable to leak through the mouth plate.
In order to resiliently support the mouth plate, one of the middle plate is replaced by a plate 11 with beads 12 at the portion N of the gasket, which is disclosed in Japanese Patent Publication (KOKAI) No. 59-90745.
In U.S. Pat. Nos. 4,791,897, 4,803,965 and 4,809,653, one of the middle plates is provided with different kind of beads on and around the portion N to support the mouth plate L and seal therearound.
The gaskets as proposed by the patents operate as intended. However, in case the portion N of the gasket need not be compressed strongly by beads, the portion of the middle plate where the beads are formed is cut, to which a compressible material is disposed for supporting the mouth plate L.
When the engine is started, large force is applied to the mouth plate L to thereby strongly compress the compressible material, the wire ring and a cured portion around the wire ring under the mouth plate L. This force is concentrated at a border between the mouth plate and the cylinder head, which results in damaging the curved portion around the wire ring. The curved portion may be broken or partly cut by the force applied to the mouth plate L.
Accordingly, one object of the invention is to provide a steel laminate type cylinder head gasket, which can securely support a mouth plate even if high pressure is applied to the mouth plate.
Another object of the invention is to provide a steel laminate type cylinder head gasket as stated above, which can securely seal around the cylinder bore and the mouth plate while resiliently supporting the mouth plate.
A further object of the invention is to provide a steel laminate type cylinder head gasket as stated above, which can easily and economically manufactured.
Further objects and advantages of the invention will be apparent from the following description of the invention.